The invention relates to brake mechanisms for electric motors and the like, and more particularly to anti-rattle mechanisms for such brakes for reducing rattling of the friction disc during rotation of the motor shaft.
The invention arose during continuing development efforts relating to motor brakes, including those known as solenoid actuated brakes (SAB), and armature actuated brakes (AAB) such as Stearns 310, 320 and 333 series brakes, offered by Stearns Division, Rexnord Corporation, an Invensys Company, and such as shown in U.S. Pat. Nos. 4,042,077, 4,181,201, 4,798,269, 5,186,287, 5,421,436, 5,437,351, 5,620,065, 5,685,398, 5,697,473, incorporated herein by reference.
A brake mechanism for an electric motor selectively stops and permits rotation of the rotary electric motor shaft. The shaft has a hub rotating therewith about the axis of the shaft. A friction disc is mounted on the hub in keyed relation for rotation therewith and is engageable with a pressure plate for stopping rotation of the friction disc, to stop rotation of the hub and shaft.
It is known in the prior art to provide noise-suppressing hub stabilizing springs between the hub and friction disc to apply a slight radial force therebetween to take up backlash and muffle noise by minimizing rattling of the friction disc during rotation of the motor shaft. Examples are as follows: U.S. Pat. No. 4,798,269 at spring 92; U.S. Pat. No. 5,186,287 at springs 174, 176; U.S. Pat. No. 5,421,436 at spring 142; U.S. Pat. No. 5,437,351 at spring 88; U.S. Pat. No. 5,697,473 at spring 142. Spring loaded ball devices are also known in the prior art.
The present invention provides a simplified anti-rattle mechanism of significantly reduced manufacturing cost. In the present invention, the friction disc includes an anti-rattle portion integrally molded therewith. In a first embodiment, the friction disc has a cavity along its inner circumference facing the hub, and a cantilever finger extending into the cavity and engaging the hub and providing a cantilever bias along a radial biasing direction transverse to the axis of rotation of the motor shaft and which urges engagement of the hub and the friction disc to minimize rattling of the friction disc during rotation of the shaft. In a second embodiment, a bump on a slotted inner circumference of the friction disc provides the biasing portion, or may be spaced from the hub by a nominal clearance. In the first embodiment, the anti-rattle biasing portion flexively applies bias. In one version of the second embodiment, the anti-rattle portion compressively applies bias. In another version of the second embodiment, the anti-rattle portion is spaced from the hub by a nominal clearance, to accommodate tolerance deviations between the hub and the friction disc at opposite ranges of their manufacturing tolerance windows, to allow insertion of the friction disc onto the hub without undue friction interference. In a preferred form of the second embodiment, the hub is provided by a hubbed configuration integrally formed on the motor shaft, eliminating the need for a separate hub member. The hubbed configuration motor shaft may also be provided in the first embodiment. In each embodiment, the friction disc is a one-piece unitary integrally molded member including the anti-rattle portion, eliminating the need for a separate anti-rattle spring.